Several of the magus class features involve casting spells from the magus spell list. They do not specify that the spell must be prepared, or cast with magus spell slots.
As a full-round action, he can make all of his attacks with his melee weapon at a –2 penalty and can also cast any spell from the magus spell list with a casting time of 1 standard action (any attack roll made as part of this spell also takes this penalty).
At 2nd level, whenever a magus casts a spell with a range of “touch” from the magus spell list, he can deliver the spell through any weapon he is wielding as part of a melee attack.
Magus Arcana and Knowledge Pool use similar language.
Now suppose a magus can cast Shadow conjuration using non-magus features (such as by multiclassing or as a spell-like ability).
Shadow conjuration can mimic any sorcerer or wizard conjuration (summoning) or conjuration (creation) spell of 3rd level or lower.
Or alternatively, they cast Shadow evocation:
You tap energy from the Plane of Shadow to cast a quasi-real, illusory version of a sorcerer or wizard evocation spell of 4th level or lower.
Shadow conjuration/evocation are not on the magus spell list. However, there are multiple conjuration and evocation spells shared between the wizard and magus spell lists, which could mean simulating conjuration or evocation spells from the magus spell list.
Could a magus use Shadow conjuration/evocation with Spell Combat (or other magus features) by simulating a spell from the magus spell list?